Method of assembling spark plugs



Dec. 19, H. RABEZZANA METHOD OF ASSEMBLING SPARK PLUGS Filed Jan. 4, 1930 2 Sheets-Sheet 1 gig. 1

Patented Dec. 1'9', 1933 ,Y y1,940,323 METHOD F ASSEMBLING SPARK PLUGS Y 'f ,Hector Babezzana, Elint, Mich., assigner to A C Spark Plug Compa-ny, Flint, Mich.; a company Application January 4,- 1980. Serial No. 418,572 p V1o claims. (C1. isf-59) This invention'relates to the manufacture :of

. spark plugs such as are used in the ignitionsystem of Vaninternal combustion engine and more particularly to an improved method of assembling the center electrodey in the insulator core." According to customary practice the center electrode is held inthe core by suitablecement which also seals'the boreagainst leakage of gases from the engine combustion chamber. To provide an improved method of assembly suitable for high speed production and one which will insure a tight seal is one of the primary objects o! the `present invention.V To this end there is contemplated, in a preferred embodiment, the use of a-center electrode having an enlargedscrew threaded head at lts upper end for threaded engagement within an enlarged portion of the insulator bore. `The assembly operation proposed invalves the insertion Vof the Velectrode wire in theA herewith the head screwed partly `into place and then the injection under pressure of, sealing cement into the bore and around the, electrode to mi the bore, and finally the movement of theelec-Y trode to its proper operative position by screwing home the head thereof, whereby the cement within the bore is compressed and packed between the electrode and insulator core to completely ll all voids and eliminate air pockets and the like which would otherwise lessen or destroy fm? the "eiectiveness of the seal, reduce heat transference between the electrode and core and cause rapid deterioration of the sealing material and Pluwfis- N YApparatus is shown in the accompanying drawings for performing the assemblyA operation, but it will be understood that various types of machines-may be employed including those that are entirely automatic. A machine suitable for production work is shownV with parts in section in Figure' 1. The sectional view Figure y2 shows a device that may be used for slow hand work. An enlarged detail sectional view, Figure 3, illustrates a part of the machine of Figure 1.

Figure 2 illustrates an arrangement for practicing the invention which was used experimentally but which is also adapted for small production work. In this case the insulator core 'indcated by 1 is secured ln the usual metal shell 2, the lower end of which is screw threaded for 5s screw threaded head s at the upper end with an engagement in the spark plug opening of the en` intermediate abutment collar 7, that portion of the head above the collar being intended for the attachment of the usual lead wire or cable of the ignition system. Y Y

These'parts are rst assembled to the position 30 illustrated in Figure 2. That is, the center wire 5 is introduced in the bore 3 of the core and head `6 Vis partially threaded into the opening 4. With the parts in this relation, the shell 2 is threaded into ank opening or pocket 10 in a 55 metal .block or .diel'lL which previously has been filled with a suitable cement preferably in a semifluid 0r plastic state. Upon downward movement ofthe spark plug assembly, as the shell is rotated .and engaged with the threads of the 70 opening 10, the plastic sealing material is compressed in the die and caused to flow upwardly into thebore 3 of the core and around the electrode' wire into the space provided by the enlarged portionfl to'thereby completely ll the 75 space inthe bore unoccupied by the electrode. Ob'servance of the cement oozing or seepng out around the screw threads at the upper end of the core ,gives an indication that the bore is completely filled. Rotation is then stopped and 90 the shell can either be left in this position for the time being or completely removed from the die 11, while the head 6 is threaded down until the collar 'l .abuts .or contacts tightly with the top `surface of the core. It will be apparent Ythat the final movement of the electrode tightly compresses or packs the'cement in the bore and particularly in the enlarged portion thereof, to get rid of any air' pockets that may have been formed and tightly lill the whole space, thereby assuring a tightA seal. After the excess material clinging to the Vbottom of the plug has been washed away nand the cement in the bore given time to dry out and harden, the plug will be ready for use. k

The machine shown in Figure 1 has been designed Ior production purposes and in this case the electrode is preferably assembled in the core prior to the time the core is placed in its metallic shell. This machine .consists of a reservoir or container 15 for the sealing material, carried by a work table 16 and having a drain plug 17 inrits bottom wall and a removable cover 18. Projecting downwardly lfrom the Vcenter of the coverV is a stem or shaft 19 having pvoted at 105 its vlower'end a rock shaft 20. 'One .end of the shaft 20 is connected by the link 21 extending through a stufling box 22 in the head or cover 18 withl a lever 23 which in turn is connected through a link 24 with an actuating lever 25 110 which may be pivoted to the floor through a bracket 26 for depression by manual elort exerted through the foot of the operator. A contracting spring 27 may be provided to manually hold the lever in retracted position. The opposite end of the rock lever 20 carries a stem 30 projecting upwardly through the stand-pipe 31 secured to the cover 18 by the nut 32 and having at its upper end a valve head 33 that projects through a central opening of the guide plate or ring 34. In the drawing the valve is shown in open position, but it is normally held over the opening in the seat 35 secured in position by the nut 36, vwhich also carries through fitting 37, the discharge nozzle 38 over which the lower end of the insulator core 1a. is adapted to seat. Compressed air or other fluid under pressure may be led to the top of the chamber 15 through a conduit 40 from a suitable source of supply to lift the sealing material in the stand-pipe 31 to the discharge nozzle when the valve 33 is opened.

` Mounted above the pressure discharge mechanism is a reciprocatory device under manual control and including a carrier or frame 42 having a pair of spaced apertured arms 43 and 44 `slidably mounted on a post 45l and carrying an electric motor 46. This frame is movable downwardly by a hand lever 48 pivoted at an intermediate point to the frame and at one end connected by the shackle 49 With a collar 50 xed to the rod 45 as by means of a set screw 51. A coil spring 53 interposed between the xed collar and apertured arm 44 serves to yieldingly maintain the frame in its uppermost position. Extending downwardly through the dependent hub 55 of the motor housing is a spindle 56 carrying a chuck 57 in which is removably secured a spinner 58. Different sized spinners may be secured in the chuck in accordance with the type of the spark plug to be assembled. This spinner is intended for frictional engagement with the collar 7a to rotate the same and screw the head 6a of the electrode in the enlarged bore at the upper end of the core. The core vis f clamped over the discharge nozzle 38 by a collar 60 interchangeable with other collars to accommodate different sized plugs, in the aperture plate or disc 61, which may be welded or otherwise secured to a slidable sleeve 62 keyed for Y telescopic engagement with the sleeve 63, as by means of set screws 64 threaded in the sleeve 62 and projecting into elongated slots 65 in the sleeve 63. The upper end of the sleeve 63 is split so that it may be contracted and held on the hub 55 as by means of a clamp collar 67, an expansion spring 68 being interposed between the collar and the sleeve 62 to yieldingly urge the sleeve 62 downwardly. Thus the sleeve 62 is keyed to the xed sleeve 63 and so prevents rotation of the core 1a., while it is movable axially to accommodate the descent of the spinner 58 as the electrode is threaded home. Observation openings 70 are provided in opposite sides of the sleeve 62 and 63 to allow the operator to view the progress of work.

brought into engagement with the electrode col-` lar 7a- If the electric motor is now actuated the. electrode may be partially screwed into the bore,

after which the foot pedal 25 may be depressed to allow the sealing material to enter and ll the bore until the operator observes leakage around the screw threads at the upper end when the valve is again closed and the motor actuated once more to spin the electrode into nal position and thereby compress the sealing material introduced into the bore.

It will be obvious that structural details of the assembling machines may vary widely and that the invention relates particularly to the method of injecting sealing cement into the bore with the electrode partly in place and then compressing the sealing cementrby the further manipulationof the electrode to its nal operative position.

I claim:

1. The method of assembling an electrode in a spark plug core comprising the positioning of the electrode partly in the core bore, then injecting into the bore a sealing material and nally packing the sealing material .by completing the Apositioning of the electrode in the bore.

2. The method ofuassembling an electrode in a spark plug insulator comprisinginitially. screwing the head of the electrode in the. upper end of the insulator for a part of its length, to partially ill thespace in the bore, then completely filling the remaining space of the bore with sealing cement under pressure, and finally packing the cement by screwing the headV of thegelectrode home.

Y 3. The method of assembling an electrode in a spark plug core, including the partial insertion of the electrode in the bore of the core, the injection of sealing material in the bore and the completion of electrode insertion.

4. The method of assembling an electrode in a spark plug core, including starting the insertion of the electrode in the bore of the core, injecting sealingmaterial in the bore around the electrode and continuing the insertion of the electrode to completion. I l

5. 'Ilhe method of assemblingl an electrode in a spark plug core, including partially inserting an electrode in the bore of the core, injecting under pressure a sealing cementnto ll the bore and packing the cement particles by completing the insertion of the electrode.

6. The method of assembling an electrode in a spark'plugV core, including inserting a plastic sealing material in the bore of the core, and then moving an electrode thru the material to operative position to thereby pack the sealing material.

portion thereof screw-threaded, inserting in the bore an electrode having a screw-threaded portion for engagement with the threadedportion of the bore, engaging and partially threading said portions together, injecting cementitious material in the bore to fill the same and then completely threading said portions together, to compact said cementitious material.

9. The method Vof assembling spark plugs including inserting an electrode in the bore of an insulator core, then injecting cement throughrone occupied by the Iarger'section of the electrode, and then the injection of cement into the space of the bore unoccupied by the electrode and finally the crowding of the cement particles in the bore by the further insertion of the electrode to more completely occupy the space therein.

HECTOR RABEZZANA. 

